Variable capacity pump and control therefor



April 15, 1941. c. M. KENDRlcK. l 2,238,052-

l VARIABLE CAPACITY PUMP AND CONTROL THEREOR I Filed Jan. 14, 1939 6 Sheets-Shet 1 F511. ,j/ ,e

Z/ v .1 @ad/'ng fa 621/1170/ Hemer/ l imlb.

34 j, 30 43 42i u 45 I 45 4Z T- 4Z 3 9/ ,l 40

7l/, INVENoR. A 33, har/@5 M mdf/6A Ml a t ATTORNEYS.

April 15, 1941. c. M. KENDRlcK VARIABLE CAPACITY PUMP AND CONTROL THEREFOR Filed Jan. 14, 1939 GSheets-Sheet 2 INVENTOR har/e5 M. fmafr'fc/f 6 Sheets-Sheet 5 C. M. KENDRICK Filed Jan. 14, 1939 VARIABLE CAPACITY PUMP AND CONTROL IHEREFOR April 15,'1941'.

INVENTOR. Uhm/e5 M. fendr/o/f ATTORNEYS.

qri115,1941. -.M. KENDRICK 2,238,062'

VARIBLE CAPACITY PUMP `ANI) CONTROL THEREFOR Filed Jan. 14, 1939 sneets-sheet 4 Fig'. H

za/ 03 El INVENTOR.

ATTORNEYS.

April 15, 1941. c. M. KENDRlc-K 2,238,062

VARIABLE CAPACITY PUMP AND CONTROL THEREFOR Filed'Jan. 14, 1939 e sheets-snee; s.

April 15,1941. c. M. KENDRICK VARIABL CAPACITY PUMP AND CONTROL THEREFOR Filed Jan. 14, 1939 6 SheetS-Sheet 6 INVENTOR Char/25M /fend/JJZ'( I. 'x

BY v' l v Patented Apr. 15, 1941 UNITED sTATlazs PATENT oirlcf vAnIABL CAPACITY PUMP AND ooN'rnoL 'rnEnEFon Charles M. liendrick, New York, N. Y., assignor to A Manly Corporation, Washington, D. C., a corporation oi' Delaware Application January 14, 1939, Serial No. 250,864'

28 Claims.

` of fluid pressure, wherein uid pressure operated devices are supplied with fluid under pressure by variable. delivery pumps. The present invention in .one laspect relates'to variable delivery pumps .or pump units and the control thereof, and more particularly to rotarypiston pumps of the vane type having two or more sections or parts delivering uid to a common discharge and Whose capacity or output may be infinitely varied from minimumto maximum.

One object of the invention is a noveland improved variable delivery pump unit of the character indicated and control therefor, whereby a more certain, accurate and elcient control and operation of the unit is obtained.

' A further object of the invention is a pum-p unit and control therefor of the character indicated which is characterized by its eiliciency and flexibility in operation and its -simplicity in construction and assembly. f

' A further object of the invention is a novel and l `improved pump and control of the character indicated including fluid pressure means for operating and flexibly interconnecting the separate control elements of the different pump unit sec- 30 tions and a single control means for saidv iluid pressure means. r

Another object is `to provide means for controlling the total uid volume delivered by multiple pump sections or parts `into their common discharge conduit without respect to the division -of this total output between the individual pump` ing sections.

A further object is to provide a control of this character in which eachsection is provided with its individual fluid motor for actuating `the delivery-determining element thereof to vary the output of its section, the operation of vall of said iluid motors being under joint control of-a common controlling element active to regulate the combined operation of all of said fluid motors independent of the extent of operation of any one of them.

A further object ofthe invention is a novel and improved iiuid pressure system including a variable delivery pump unit and control therefor of the character indicated.

' A further object of the invention is a pump unit and control of the above indicated character including, a novel and improved fluid pressure follow-up control.- i L' Other objects of the invention will hereinafter appear.

For a better understanding of the" invention reference maybe had to the accompanying drawings forming -a part of this application wherein: Fig. 1 is a view, partly in section,`of a pump unit and control embo ng the invention;

Figs. 1a and 1b are views of an element of Fig. 1;

Fig; 2 is a sectional view taken at right angles to Fig. 1y along the line 2-2 thereof;

Fig. 3 is a sectional view indicating the pump unit chambers and circuits taken along the line '10 3 3 of Fig. 2;

Fig. 4 `is an enlarged view of one of the plate elements of the pump unit showing the face thereof adjacent the rotor; 4

Fig. 5 is a sectional view to larger scale than Fig. 4 along the line 5 5 of Fig. 4;

Fig. 6 is a sectional view of a 'modified pump unit;

Fig. 7 is a diagrammatic view illustrating-a fluid f pressure system embodying the pump unit and 2 control of the invention together with novel means for controlling the same;

Fig. 8 is a'view of a manual control means for use with the pump unit and control of Fig. 1;

Fig. 9 illustrates a further modification em.

bodying a novel, improved hydraulic follow-up;

Fig. 10 is a diagrammatic view illustrating another embodiment of the invention; and

Fig. 11 shows a'modifled form of pump unit and control.

Referring to Figs. 1 to 4 of the drawings, I

have illustrated my invention as embodied in a rotary piston multi-section or part 4 pump of the vane type.` The pump, which is indicated generally by thenumeral I, includes a rotor 2 which is provided with a multiplicity of vanes 3. The

' vanesl are movable inwardly and .outwardly as the rotor rotates with their outer edges following ad-i justable tracks indicated generally at 4.' In the particular embodiment shown the pump is a 40 double pump comprising two pumping sections or halves which discharge into a common discharge 5. The particular structure vof the rotor 2, the

vanes 3f and the track l forms no part of. the present application but a part of my co-pending application, original led December 24, 1938,

Serial No. 247,586.I It is understood, however, that the structure of these pump parts may as sume any suitable form of double or multiple pump ofthe general character indicated, such,

, for example, as that yof either of the structures .disclosed in United States Patents 2,141,270 and 2,141,171, issued December 27, 1938. f

The capacity or output per revolution of either pumping section may be varied from minimum to maximum'by the lateral or radial movement .of its delivery determining element or adjusting rod 6,

whichV is suitably attached to a radially slidable member 'l carrying the` adjustable track 4 as, for example, by means of a pivot pin 8. The member 1 is slidably mounted in a recess yor opening 1' "formed in a spacer ring 9 on the interior of the casing. In the embodiment shown the output of either pumping section is increased by movement of its delivery determining element 6 in an outward direction with respect to the axis of the -rotor and the output is decreased by the inwar embodiment shown, as a part of the casing of the pump. The fluid pressure tending to move the piston track 4 andthe delivery-determining element 6 outwardly, and is also opposed by a coil spring I2, the inner end of which rests upon a seat on a stop ring lll and the outer end otwhich engages a ange I4 formed on the enlarged outer end I5 of the delivery-determining member 6. The enlarged part I5 of the delivery-determining element and the coil springv I2 extend up into the sleeve of the Apiston IIl and a bearing member I6 is provided between Ithe piston and the delivery-determining element having a at outer surface I1 in engagement with the piston and an inner spherical surface I8 in engagement with a correspondingly curved surface at the bottom of a recess formed centrally of the enlarged part I5. A clearance is provided between the side walls of the bearing member I6 and the side walls of the recess, as indicated. In the particular embodiment shown a clearance I 9 is provided between the delivery element 5 and the walls of the opening through the spacer ring 9 and the stop ring 40 to avoid binding in the operation of the delivery-determining element, and further to vmaintain communication between the inner part of the cylinder II and the recess 1 in which the member 1'slides.

The outer ends of the cylinders II are connect-A ed through a communicating passage or pipe system 20 containing an incompressible fluid such, for example, as oil, etc. In order to control the pump delivery per revolution incompressible iiuid is admitted to or withdrawn from the communicating passage 20 and the cylinders II. This admission and exhaust of fluid for this purpose is I0 inwardly is opposed by the uid pressure inside of the pump tending to move thepoints of the casing. This admissionand exhaust is under the control of a single common mechanism which, as indicated, may be either manually or automatically manipulated.

In'the particular embodiment of pump structure shown (Figs. 1, 2, 3, 4 and 5) ,the pump casing is in two axially separable parts 22 and 23, being suitably fastened together as by screws 24,

and a pair of mating end plates 25 are disposed on the opposite sides of the rotor and between the rotor -and thecasing parts, the end plates being axially positioned by the spacer ring 9. 'I'he intake conduit 5I is suitablyconnected with the pumps intake 26 which branches to form an intake channel or chamber 21 in the pump casing for each half or pumping sectiony of the pump.

Each intake channel 21 is connected by an ap-' propriate passage and port, as indicated partly by the dotted lines at 38 in Fig. 3, with the corresponding arcuate intake port 21' formed in the end plate adjacent the side wall of the casing .23. The space between adjacent vanes is effected through a branch pipe or passage 2|" which leads to either a manual or other control, as will hereinafter be described more particularly.

The piston I0 and corresponding delivery-determining element 6 of each of the pumping sections is subjected on'one side, through the hydraulic passage 20 and the other piston, to thefluid pressure generated in the other pump section, and on the other side to the pressure being generated 'by its pump section and the spring I2, the piston and the delivery determining element being balanced and floating between these forces. v

Thus, by the construction and arrangement Shown, each of the pistons IB and its corresponding delivery-determining element 6 is at all times oatingly balanced between the pressures generated in the two halves or sections of the pump and each is independently movable to assume the balanced condition or position, without binding or undue strains upon any of the parts. The delivery per revolution may be iniinitely and accurately varied and controlled through the simple mechanism shown, merely by admitting iluid pressure to or exhausting it from 'the common ders II disposed at the diametrically opposed iilled with fluid as said vanes sweep across the intake ports 21' and this fluid is discharged as the vanes move past the arcuate outlet port 28 of each pumping sectlon; the work of pumping is accomplished as the vanes move. across the pumping arc on e radially inner end of each of the slidable mem into the arcuate ports.28 passes through appropriate passages and ports in the casing, which are likewise indicated in Fig. 3 partly in dotted lines at 39, into the common annular discharge channel 28 which in turn is suitably connected with the pump outlet 5 into thedischarge con-V duit, 53. Each half or pumping section of the pump thus comprises a separate pumping unit having its own intake and discharge areas, but both halves discharge their pumped fluid into a common discharge conduit and preferably take their supply of fluid from a common 'inlet conduit as shown. It will be understood that the 'I'he end plates 25 are also provided with twopairs of arcuate vane slot ports 29 and` 29 respectively which are adapted to register lsuccessively with the inner ends of the vane slots as the rotor revolves. The vane slot ports 29 are connected with the arcuate ports 21 of the corresponding end plate 25, as by radial grooves 35 formed on the outer faces of saidv end plates, and similarly the vane slot ports 29' are connected as by radial grooves 36 with the outlet ports 28' of said end-plates 25, The arrangement is such that the inner endsof the vanes are supplied with uid having the same pressure as that acting on the exposed outer ends thereof while said vanes are passing across the intake ports 21 and the outlet portsA 28' of .the two halves or pumping sections, so that said'vanes are hydraulicallyV rs 1. Fluid thus dischargedl pumping section. Each stop ring are also connected as by radial passages 31 with the holes at the center of said end plates through which the rotor hubs'pass to provide return passages for leakage. Diametrically opposed abutments 30 separate the two halves of the pump from each otherv in the conventional manner. At least one of the end platesl 25 is rabbeted on its innerside around its peripheraledge to form an annular chamber as indicated at Il, and a radi-- ally disposed groove or-channel 32 is formed to connect the annular chamber thus formed with one of the suction ports 21'. 'I'he chamber 3l overlaps slightly the recesses I formed in the lining member 9. ,'Each of the cylinders II is thus in communication at its Ainnerends at all times with the suction port for the pul'POse of keeping the pressure of the iluid at the inner ends of the cylinders at a relatively lowvalue substantially equal to the pressure oi' the fluid in the intake ports 21' and also for the purpose of providing means by which fluid leaking past the slidable members 1 is returned to the intake port.

' As'above indicated, each stop ring lll is provided with a clearance hole at its center (Figs.

la. and 1b) through which passes the corresponding delivery-determining element 6. To facilitate manufacture ofthe parts, the stop ring 40 is also preferably formed with a cylindrical outer contour and is. located in an appropriate bore formed in the casing member 23 as shown in Fig. 1. Each stop ring 40 is adapted 'to bear y against and be positioned upon the outer cylindrical surface of the spacer ring 9- and is accordingly provided with an arcuate surface Il (Figf 1b) having the same curvature as that of the periphery of said spacer ring. This arcuate surface 4I is preferably of the same width as that of the spacer ring 9 in order that the stop ring 40 may be positioned solely thereon and for the added purpose of preventing any contact between said stop ring and the end plates 25which might distort or displace the latter; outer areas, adjacent the arcuate surface Il, are accordingly relieved as indicated at I2 in Fig. 1b. A transverse groove or passage 43 is also provided to connect the relieved areas 42 with the clearance 3 spacer ring 9 have outstanding advantages. As already stated, the stopring is free to adjust itself upon the spacer ring 9 in alinement with the other parts, thereby decreasing any tendency toward "cooking action or binding. Use of the stop ring to determine'maximum inward posimining element 8 tion of the corresponding delivery-determining element 6 not only provides a simple yet accurate means of accomplishing this result but further makes it possible to alterthe maximum possible inward position of said delivery-deter- (thereby correspondingly changing the minimum output of the pumping section) byv merely substituting another stop ring of different thickness. The free-floating or selfalining relation between each piston Il. and its corresponding delivery-determining element provides greatly reduced cost as-compared with rigid or non-self-adjusting constructions or relationships; with the construction as described, errors in manufacture do not cause binding of the parts which are moved to alter so that it is not necessary to work to precise hole at the center of the stop 'ring in order to assure uid connection at all times between said clearance hole and the recesses 3|- of the end plates 25. A's. already stated; thestop ring-'ll forms a seat for the inner end of its corresponding coil spring I2, and the spring I2 thus holds the stop ring 40 in proper alinement with the other parts, which alinement is facilitated bythe ability of the stopring to adjust itself circumferentlally with respect to the outer surface of the spacer ring 9.

'I'hestop rings III tant function, from which they take their name, that is to say, each stop ring limits the maximum inward movement determining element 6 and'hence limits the extreme inward position of the corresponding slidable member 1, thereby limiting and rdetermining the minimum output of -the corresponding is accordingly provided with a surface u (Fig. 1a) adaptperform still another impor- A of its corresponding deliveryed to contact the shoulder I3 on the enlarged 'end of its delivery-determining element l to thus limit the m ximum inward movement thereof.

Theonstruction and co-operating arrangemeutv o theadjusting pistons I0, bearing members 96, delivery-determiningelements or adustlng rods 6, stop rings 4I, springs I2 and under iniiuence dimensions,'whereas without this construction sure cylinder construction Vwherein 'the piston I0 is provided with a center projection I0' extend-v ing down into the sleeve a short distance, against which abuts the bearing members I6. The packing II yissecuredto the end of the piston by means of a washer 33 and a single DOsed boit 33'. A

As already indicated, the simple structure pre.- viously described enables 'control of the pumps output to .be e'ected `by regulating the volume of uid admitted to or withdrawn from the branch Pipe or passage 2|. This admits of the use of a'wide variety of controls for regulating the admission of iiuid through or lwithdrawal of fluid from the passage 2|, and in order that this may be fully understood theinvention is illustrated in connection with controls in which such admission or withdrawal are effected entirely by manual means, and in connection with controls in which such admission or withdrawal are effected by difference between the pressure of the fluid in the passage 20 and in other parts of the iluid's'ystem and in which a1one,`or by hydraulically-actuated mechanism in turn under control of manual means, or by hydraulically-actuated mechanism in turn under control of automatically-acting means.'

In Fig. 7, for example, I have shown my invention as embodied in a fluid pressure system including a iiuid pressure operated device M, a multiple or double section pump I, fluid pressure adjusting cylinders II for -adjusting the outputs of the-pumping sections, a single element |52 hydraulically-actuated to regulate the withdrawal or admission of fluid to or from the passage 2| of pressure dierences in t-he passage 20 and elsewherein the fluid system, a

variable oriiice which may be opened or closed,`

either manually or otherwise, to cause regulating the pumps output centrally dissuch withdrawal or` admission are regulated either -by manual means Iarated by the reduced portions |55 and ce 10 for maintaininga predetermined xed output corrected for changes in viscosity.

- The pump I of Fig. 7 is similar to that of Figs. A

l,v 2, 3, 4 and 5 but it is somewhat schematically illustrated for convenience. A portion of its discharge conduit 53 leads to the fluid motor M and fluid discharged by said the reservoir 52 through the portion 55 oi' said discharge conduit. With this arrangement, motive fluid delivered by the pump I operates the fluid motor and the operation` of the latter is controlled by varying the output of said pump I.

Thecapacity or output of each pumping section may be infinitely varied from minimum maximum by lateral movement of its delivery determining element or adjusting rod 6 as vdescribed above. Each adjusting rod 6 is independently movable to regulate and control a portion of the total output of the pump that is to control the output; of its pumping section. For

example, if the output of the pump I is 20 gallons per minute at a particular speed, each adjusting rod 6 would be independently movable to control an output of 10 gallons per minute if .the

total maximum output of the pump I is equally divided between its two pumping sections.

The valve mechanism'illustrated in Fig. '1 includes a valve piston |50 slidably fitted within the valve bore |26 of the valve housing |25 and having three heads |I, |52 and |53 respectively, sep- |56. The head |52 covers the cylinder port |21 when the valve piston |50 is in its neutral position in which it is shown in Fig. 7. Movement of the valve piston |50 to the right of its neutral position connects the cylinder port |21 with the portion of the valve bore surrounding the valve pistons reduced portion |55, so that fluid may be exhausted from the passage 20 and the outer ends of the adjusting cylinders I I, such exhausted fluid returning to the reservoir 52 through the passage 59.

The adjusting pistons I0 move outward under the influence of the springs I2 and pump pressure when the outer ends of the adjusting cylinders and passage 20 are thus connected with the exhaust, as already explained.

Movement of the valve piston |50 to the left of its neutral position connects the cylinder port |21 with the portion of the valve bore |26 surrounding the valve pistons reduced portion |56; pressure fluid supplied to this portionof the valve bore |26, as through the passage 58, may

then pass around the reduced portion I 56, through the cylinder port |21 and the branched passage 2| to the common passage 20 and outer ends of the adjusting cylinders causing the adjusting pistons I0 to move in an inward or delivery decreasing direction. In this connection it may be pointed out that pressure of iiuid in the passage 20 will always be less than the pressure of the fluid in the discharge conduit 53 except at extremely low pressures; this is due to the fact that the areas of the' adjusting pistons I0 exposed to pressure of fluid in the adjusting cylinders are greater than the areas of the inner en-ds of the slidable members 1 which are exposed to pump pressure. The valve head |52 is shown as provided with a number of conventional V- notches on its end adjacent the reduced portion |56, these notches providing a relatively gradual connection between the reduced portion |56 and the cylinder port |21 when the valve piston |50 moves to the left of its neutral position, thus reuid motor passes into 'reducing or eliminating any ducing any tendency toward abrupt movement of the adjusting pistons I0.

In some instances it has been found desirable to provide a centering mechanism for the valve piston to assure its proper location with respect to the other parts when said v alve piston is in its neutral position and for the further purpose of tendency toward hunting or surging that may be present. A centering mechanism suitable for this purpose and of conventional type is illustrated in Fig. 7.

. As here shown, the centering mechanism is located in the bore' of a housing 80 which vis suitably attached to the right hand end of the valve housing |25, 'as by threaded engagementtherewith. The outer end of the housing 80 is in turn closed by an auxiliary valve housing 80, the purpose of which will be later explained, and the two parts are appropriately fastened together, as by `the screws 92. It is preferable that there be substantially no pressure of any fluid that may enter the bore of the housing 80, as through leakage, and a passage 93 leading to the reservoir 52 is accordingly connected withl said bore.

The centering mechanism includes a pair of washers or annular members 8| and 82 freely slidable upon a rod 83 which is of smaller diameter than that of the valve piston |50 to which it is securely attached as by the pin 84. A relatively light compression spring 85 is positioned between the two washers 8| and 82 and urges them toward the stops or seats 81 and 88 formed respectively by the end of the valve housing |25 and the reduced 'end portion of the bore of the housing The arrangement is such that when the valve piston |50 is in its neutral. position the washer 8| is in contact both with its seat 81 and with the adjacent end of the valve piston |50; and similarly, the washer 82 is then'in contact with its seat 88 and is also in contact with the adjacent end of the auxiliary valve piston |54 which is carried by the rod 83 and is positioned with respect thereto by the nut 86 on the threadedend of said rod 83.v e

The washers'8l and 82 thus move toward each other, upon further compression of the spring 85, f

and one or the other of them is so moved whenever the'valve piston |50 moves out of its neutral moves the washer 82' toward the left and away from its seat 88, the washer 8| remaining against its seat 81 as the rod 83 slides through the hole at its` center. In this manner the centering mechanism tends to maintain the valve piston |50 in its neutral position and presents a relatively slight increased resistance to displacement of said valve piston in either direction.

Ihe valve mechanism of Fig; 7 also includes an auxiliary valve bore formed in the auxiliary valve housing 90 and of the same diameter as the valve bore |26, into which the auxiliary valve piston |54 is slidably tted. The auxiliary valve bore is thus equivalent to a continuation of the valve bore |26 and the auxiliary valve piston |54 is likewise equivalent to an additional head on the valve piston |50. The valve piston |50, rod 83 and auxiliary valve piston |54 may thus be said to comprise the valve piston assembly.

The left hand -end of the valve piston |50 projects beyond the end of the 'valve housing |25 spring 14 having abutment pieces 15 and ^96 respectively on each of its ends. The abutment piece 96` bears against the adjacent end of the valve piston |50 and the abutment piece 15 bears against the end of the screw 16 which extends through the closed end of the housing 95 andprovides means for adjusting the compression of the spring 14. As will be readily understood, the spring 14 exerts a force upon the valve piston |50 tendingv to move the valve piston assembly toward the right as viewed in Fig.. 7 and the abutment piece 96, which is of larger diameter than that of the valve bore |26, limits the maximum distance in this direction to which said valve piston assembly can be moved by said spring 14. y

The position and movement of the valve piston assembly, by which the output of the pump I is regulated, are determined and eiected by the actual drop existing across the metering oriicev 80 relative to a predetermined pressure drop thereacross. 'Ihe orice 80 is here shown as positioned in the portion 55 of the discharge conduit and the end of the auxiliary valve housing 90 is accordingly connected, as by the passage 82' with said portion 55 .ofsaid discharge conduit at a point on the inlet side of said orifice '80. It has been found that when the metering orice 80 is positioned at a point in the discharge conduit intermediate the driven member 54 and the reservoir 52 the pressure of the fluid on the outlet side of the orice 80 is so small and `subject to such minor variations that in practice it may frequently be neglected. `In other words, the actual amount of the pressure existing on the inlet` side of the orifice 80 may alone be practically employed in many instances as the measure of the pressure drop across said orice and hence may be alone employed in measuring the rate of uid flow therethrough-.The outlet side of the orice 80 is therefore not connected with the valve mechanism in the arrangement of Fig. 7. 'I'he force exerted 4upon the valve piston assembly by the action of the pressure fluid from the inlet side, of the orifice 80 upon the end of the auxiliary |54 is thus opposed only by the force valve piston of the spring 14 when the valve mechanism is employed without viscosity compensating means. This arrangement has the advantage of simplifying the structure and of reducing the necessaryv l uid connections.

Withv the pump I continuously driven, the valve-mechanism of Fig. 7 functions to jointly control movement of the two adjusting pistons Il),v whereby a definite youtput maintained foreach adjustment or extent of opening of the variable metering orifice 80. This is accomplished through use of the pressure drop across the orice 80 to measure the rate of fluid ilow therethrough, the pressure existing onvthe inlet side ofksaid orice 80 being alone employed for this purpose in the present instance as hereirrbeforestated. In Fig. 7 tile valve piston assembly is shown in its neutral position in which -the head |52 closes the cylinder port 21, therebycompletely cutting oi communication between the passage 20 connecting the outer ends of the adjusting cylinders I I and the valve bore |26. The parts will remain in the position as crease in pressure,

stored to its neutral position an'd will considered constant or neglected, it will be understood that the pressure existing on the inlet side of the orifice 8l (for any setting r'adjustment of said orice Il and of the compression of the spring 14) will depend entirely upon the rate' of fluid Iiiowtherethrough and hence will depend entirely vupon the output ot the pump I. It will also be understood that the valve piston assembly will remain in' its neutral position as long as the output of the pump I remains constant atan amount producing the pressure on the inlet side of the oriiice I0 required to balance the opposing force exerted by the spring 14. Increase in the output of the pump I, as because of increase in its speed or for any other reason, will of course produce an increase in the pressure existing on the inlet side of the orifice 80. This increase in pressure will be immediately. communicated to the end of the Ibore in the auxiliary valve housing 90 where it will act upon the auxiliary valve piston |54, causing the valve piston assembly to move toward the left as viewed in Fig. 7 This movement vof the valve piston assembly cnnects the cylinder port |21 with theportion of the valve bore |26 surrounding the reduced portion |56 `of the valve piston; pressure uid'from the passage 58 is thus admitted to the outer ends of the adjusting cylinders II, forcing the adjusting pistons Ill inward or in a delivery-decreasing direction and thereby reducing the output of the pump I.

The pressure existing on the inlet side of the orice will, of course, decrease conformably with and immediately upon decrease in the output of the pump I responsive to the corrective action Just described.

the .spring 14 will correspondingly and simultaneously move the valve piston assembly toward the right as viewed in Fig. 7. Decrease in the output of the pump I accompanied by corresponding movement of the valve pistonv assembly toward the right, will continue until the delivered volume is reduced to the exact amount producing the pressure on' the inlet side or the orice 80 as established by the spring 14 when the valve piston assembly will be reagain stabilize the adjusting pistons I0.

'Ihe operation of the ,mechanism is, of course, the reverse of that above explained when the output of the pump IA is -for 'any reason decreased below the amount` at which the corresponding pressure existing on the inlet side of the orifice 80 balances. the force exerted upon the valve piston assembly in its neutral position by 4the spring 14. Upon such decrease, the valve piston assembly will be displaced from its neutral position and moved toward the right by the spring 14. 'I'his movement of the valve piston assembly will connect the cylinder port |21 with the portion of the valve bore |26 surrounding the reduced portion |55 of .the vvalve piston, and hence will permit emission or uid from the passage 20 and the outer ends of the adjusting cylinders Il.. The adjusting pistons I0 will immediately be moved outward or in a delivery-increasing direction,under iniuence of the pump pressure and the springs I2 as far and tsrapidly as permitted by exhaust of fluid. This- Responsive to this decase of the fluid pressure on movement of the adjusting pistons IA will continue until the output of the pump I has been restored to the amount producing the pressure l on the inlet side of the orice 80 as determined operation upon slight departures from the output to be maintained. y

From the foregoing it will be .understood that there is' only one rate of fluid flow through the orifice 80 (viscosity being neglected or considered -as constant) that will produce a predetermined amount of pressure on the inlet side of the orifice 80 4for any adjustment or extent of fopening thereof, and hence there 1s only oneoutput of the pump I whichv meets this requirement; that is to say, there is only one volume of fluid delivered by the pump I into the discharge conduit 53, regardless of pressure in the portion of said conduit 53 intermediatethe pump I and the motor M. It will therefore be seen that the control mechanism of Fig. 'I functions to so control joint operation of the two adjusting pistons I0 that a predetermined output of the'pump I is maintained for each particular setting or adjustment of the :Spring I4 and the actual output of the pump I being instantaneously altered to correct for any variations from this predetermined output. The output of the pump I is vthus held substantially constant regardless of variations in operating conditions as long as the setting or adjustment of the spring 14 and of` the oriiice 80 remain unchanged. Moreover, this holds true for' any adjustment of the orice 80 to control the motor M, and there is an instant response to any such adjustment to change the pumps delivery accordingly which changed delivery is then maintained constant until a further variation in the size or extent of opening of the orifice 80 is made.

In the foregoing explanation the viscosity of the circulated fluid has been neglected or considered as constant. In practice, however, the viscosity and the adjustments are I of the orifice SII,`

of the fluid (usually oil) will change over va relatively wide range upon change in the temperature of the uid and will noticeably affect the pressure on the inlet side of the orifice 80 resulting from a constant rate of fluid flow therethrough for any particular adjustment of extent of opening of lthe orice 80. This change in pressure on the inlet side of the orifice 80, due to viscosity change, will in turn affect the output of the pump I unless compensation therefor is provided. Fig. '7, therefore, also illustrates viscosity compensating mechanism for this purpose,

-The viscosity compensating mechanism includes a constant capacity pump 61 receiving its fluid supply through an inlet conduit 68 connected with the Vinlet conduit 5I which leads to the pump I, so that uid of the same viscosity is supplied to both of these pumps. The pump 51 is also provided with a discharge conduit 69 leading to the reservoir 52 and'having a metering orifice 10. Fluid from the inlet side of the xorice 'I0 is admitted to the bore of the housing 95,'which also serves as a compensating` cylinder, where it acts, through the abutment piece 96. upon the exposed end of the valve piston and thus supplements the force exerted by the spring 14. As in the the outlet side of the orifice of Fig. 1, it `has likewise been found vthat the pressure on the outlet side of the orice -10 may be neglected for most practical purposes. The pressure existing on the inlet side of the orice 'I0 is accordingly alone employed as the measure of the pressuredrop thereacross and the valve piston assembly is therefore not acted upon by iiuid from the outlet side of said orifice 10.

Pressure existing on the inlet side of the orice 10 will vary conformably with change in the viscosity of the circulated fluid. Compensation for viscosity change is thus eiected by variation in the supplementary force upon the valve piston |50 exerted by the pressure uid in the bore of the housing 95, the pressure of this fluid varying substantially with the pressure drop across the orice 'I0.and substantially with the change in viscosity of the fluid as already stated. In .this manner the amount of pressure drop to be maintained across the orifice 80 (which is determined by the spring 'I4 alone when viscosity compensating mechanism is not employed) is modied substantially in accordance with the effect 'of the change in viscosity of the fluid upon the pressure drop across the orifice 80 caused by a constant rate of fluid flow therethrough, so that the output of the pump I is unaffected by change in the viscosity of the circulated fluid,

The output of the pump I is preferably regulated by varying the adjustment or extent of opening ofthe variable orifice 80. 1n this manner the pumps from maximum, to a minimum such as zero fully closed.

when the orice V8Il is fully open, when the orifice 80 is Maximum output of the pump I can, as here-` inbefore stated, be obtained only when each of its two pumping sections delivers its maximum capacity or output, in which case both adjusting pistons. I0 and their attached adjusting rods 6 occupy their extreme loutward positions. The adjustingpistons I0 under inuence of pump pressure and the spring I2, immediately move to these extreme outward positions immediately upon full opening of the variable orifice 80. Similarly, the minimum output of the pump I (which is preferably substantially zero) can be obtained only when bothiof the two pumping sections deliver their minimum outputs or capacities, in which case the adjusting pistons III and their attached adjusting rods Ii are in their extreme inward positions. Upon full closure ofthe variable orifice 80 they pressure fluid admitted to the outer ends of the adjusting cylinders II immediatelymoves both adjusting pistons I0 and their attached adjustingfrods 6 into their extreme inward positions, as for example, against suitable stops, not

shown, thus reducing the output of both pumping sections to minimum.

Since each adjusting piston III is independently movable, it will be seen that there are an almost infinite number of combinations of relative positions of said adjusting pistons III and the adjusting rods 6 capable of producing each output rof the pump intermediate its maximum and its minimum outputs. In other words, each intermediate output of the pump I may be divided between its two pumpingA sections inv numerous proportions. In practice it has been found that,

when maximum outputs of both pumping sections are substantially equal, this division between the two pumping sections is substantially equal and that both adjusting pistons III occupy substanutially identical positions intheir paths of .inward and outward monelnenttfflative division of the output may be innitely varied tributed by each pumping section. For example,-

if Vthe oriilce 80'is adjusted to provide an output of gallons per minute by the pump. I, this voutput will be maintained regardless of the amount contributed to it by each pumping section. It

is immaterial therefore, whetlierthis output of I sage and the outer ends or the adjusting cyl;-

10 gallons per minute comprises equal outputs of 5 gallons per minute by each pumping section,

Y or whether it is comprised of 6 gallons per minute from one pumping section and V4 gallons per minute from the other, or whether it is comprised of anyother combination of outputs which total .10 gallons per minute.

'Ihe output of the pump comprising the combined outputs of its two pumping sections, may thus be accurately controlled 'throughout the entire range from maximum to This control, which is effected independent of denite control of the output of either of the' two pumpinders forcing the adjusting pistons I0 in an inward direction and thereby reducing the Ioutput of the pump ||0. It will be seen that movement of the piston 20| through any given distancetoward the right will cause displacement ofa definite amount lof uid from the bore of the master cylinder 200. 'Ihis iiuidof necessity must enter the passage'20 and the outer ends of the adjusting cylinders where it will cause joint or combined movement of the twoadjusting pistons I0 in an inward or delivery-decreasing direction, suilicient to increase the'combined volumetric 'capacities of "the. connected outer ends of said in'g sections and without control of the division u of the combined outputs lbetween the two sections (except, .of course, at maximum and mincontrol valve mechanism common to both adjusting cylinders il and which regulates the .joint operation of both adjusting pistons I0 by regu- 'lating the fluid volumeV admitted jointly to or :exhausted jointly from the passage 20, which connects the adjusting cylinders Il.

In Fig. 8 I have shown a manual means for controlling the admission and\exhaust of the iiuid to and from the passage 20 and cylinders Il. The passage 2l leads to and connects with the Abore of a control master cylinder 200 within which is a. piston 20| slidably tted. 'The piston 20| is'provided with suitable packing 203 held in place by a member 202 abutting against one end of the compression spring 204. The other end of the Spring 204 abuts against the closed end of the control master cylinder 200 and the arrangement such that the spring 204 .exerts force upon the member 203, packing 202 and piston 20| throughout the entire range of moveV outputs), is accomplished by a. lsingleA adjusting cylinders tojthe exact extent of the decrease in the volumetric capavcity of theV connected portion of the bore ofthe master cylinder 200. Joint or combined inward movement of the two adjusting pistons I0 through a definite distance therefore results from each' amount of decrease indthe volumetric capacity of the connectv'ed portion of the master Acylinders bore, and

hence the output of the pumpv is likewise de-` creased by a definite and corresponding amount. Since the adjusting pistons l0 are of lequal size and each pumping section is of equal capacity, it will be seen that'division' of this joint or comfbined movement between the two adjusting pisment thereof in the bore of the control master cylinder. The outer ends of the adjusting cylinders Il, the branched passage 20, 2| and the connected portion of the bore of the master cylinder 200 thus form a closed uid circuit which for convenience is termed the adjusting circuit.

The piston'20l is adapted to be moved toward the right, as viewed in Fig. 7, by any suitable man- `tons I0 thus producedis immaterial. For example, if the two adjusting pistons I0 move substantially equal distances, as will .usually be the I case, it will be evident that the output `of each pumping sectionwill be approximately equally diminished. If, however, one adjusting piston I0 moyes through a greater distance than the other, the output o f its pumping section will be reduced below that of the other pumping section but the combined outputs of the two pumping sections will be the same-irrespective of this unequal division; f

Upon rotation of the handwheel 201 in the opposite direction the piston 20| will be moved toward the left as far ,as permitted by the inner end of the screw 206, this movement of the piston 20| taking place under 'inuence of the spring 204 and of any uid pressure that may exist'in the bore of the master .cylinder 200. .An increase is thus brought about in the volumetric capacity of the portion ofthe bore of the master cylinder ually actuated means. In the present instance there is provided a screw 206 which threadedly engages and extends through the plug 205 which closes the open end of the master .cylinder 200,

and the inner end of said screw bears against the adjacent end of the piston 20|. 'Ihe outer end of the screw 206 is provided with a handwheel 20| bywhich it may be rotated and with a locknut 208 by which it may be fastened in any desired position.

The adjusting circuit is iilled with Aa substan tially non-compressible iluid, such for example as oil or -glycerine.

vthe portion of the bore of the master cylinder 200 which is connected with the. branched passage 2|. Fluid is thus displaced from the bore of the master cylinder 200 and enters the pas- Rotation of the handwheel- I20'! in one direction will cause movement of the 200 which is connected with the branched passage 2|. Immediately upon such increase the adjusting pistons I0 are moved outward or in a delivery-increasing direction by the pump pressures .and vby the springs l2 and the output of the pump is thus increased. The joint or combined movement of the two'adjusting pistons I0 is an amount sufcient to displace from the outer ends of the adjusting cylinders .uid equal in volume to the increase in the volumetric capacity of the master cylinder 200-and a denite and corresponding increase in the output of the pump I results. It is immaterial whether thev joint or .combined movement of the two adjusting pistons I0 is equally divided between them as will be understood from the explanation previously given. N j

It will thus be seen that 'the output of the pump I, comprisinglthe combined outputs of its two pumping sections, may? be iniinitely varied from minimum to maximumby rotation of the handwheel 201. This control is effected without definite control of the division of the combined outputs between the tw'o pumping sections (except, of course, at maximum and minimum lutputs) and is accomplished by a single common of each pumping section sections.

, movements of the two'adjusting pistons the corresponding outputs of the two pumping with the reservoir master cylinder which regulates the joint or combined movements of the two adjusting pistons l by regulating jointly to or expelled jointly from the two adjusting'cylinders in accordance with change in said master cylinders volumetric capacity. It will further be understood that there is a definite combined output of the two pumping sections for each position of the piston and hence for each position of the handwheel 201 although this combined output may be divided between the two pumping sections innumerous proportions.

In the foregoing explanation of the arrangement of Fig. 8 it has been presumed that there is a straight line relationship between movement of each adjusting piston I0 and the output of the pumping section under its control; that is to say, it has been presumed that movement of an adjusting piston l0 through .a given distance will produce the same variation in the output4 of its pumping section irrespective of the lparticular portion of the range of inward and outward travel of the adjusting piston I0 in which said movement occurs, and that variation in output is proportional to movement of its adjusting piston |0 and adjusting rod 8. The straight line relationship usually exists or is closely approximated in double pumps of the general character under consideration. 'I'he control hereinbefore described will, however, function satisfactorily when -this straight line relationship does not exist provided the existing relationship is continuous throughout the range of inward and outward movement of the adjusting piston I0 and is With the latter arrangement pensating relationship exists between the a comrelative |20 and sections, and the combined output of the two pumping sections is substantially unaffected thereby.

The -advantages of the invention are many, whether controlled solely -by manual effort, as in Fig. 8, or otherwise. No linkage of the elements 6 to a fixed point or coordinating structure is required between the two adjusting rods or their the `amount of fluid admitted the same for both pumping which are branched in Figs. '1, 8 and 11 and which lead either directly to the reservoirl or to other passages connected therewith.

The adjusting piston and adjusting rodl arrangement shown in Fig, 1 and schematically illustrated in Figs. 7, 8 and 10, in which the delivery-determining elements are moved outward in a delivery-increasing direction by springs in co-operation with -pump pressure acting on the pumping arcs of the slides 1, has many practical advantages. One such advantage is the simplicity of the fluid control circuit and of .the mechanism which maybe used for regulating the withdrawal of fluid from or admission of iiuid to the branch attached adjusting pistons I0; this greatly simplifies the structure and materially reduces cost and also makes alignment between adjusting pistons ||J which in turn facilitates manufacture, eliminates the necessity of holding all parts to extremely close tolerances and thus contributes to cost reduction. One control valve mechanism serves both adjusting cylinders, with the advantage of cost reduction and simplification. It becomes unnecessary to make both pum-ping sections of exactly the same capacity as minor vari-ations in their capacities are unimportant; the combined outputs o the two pumping sections are held to the proper amount irrespective of variation in the output of one pumping section with respect to the output of the other.

It is desirable to provide for the escape of any iiuid that may leak by the adjusting pistons l0 into the inner ends of the adjusting cylinders As explained in connection with Figs. 1-5, such leakage iiuid may be conveniently conducted back toa suction -port of the pump I through the passages 3| and 32 which are formed in the end plates 25. In the schematic arrangement of Figs. '7, 8, 10, and 11, however, the inner ends of the adjusting cylinders are shown as connected it unnecessary to provide exactv the two adjusting rods 6 or to regulate the operation of 52, as through passages |23 75 passage 2| in order to Vary and control the output of the pump. Another advantage is that there is no lost motion in the adjusting mechanism, due Vto the so-operating. relationships of the parts and 'of the forces acting upon them. For'these and other reasons I prefer to use the adjusting rod and piston arrangement as already described in connection with Figs. 1, 7 and 8, but other adjusting piston arrangements and other methods of outward actuation of the deliverydetermining elements may be employed and certain of the advantages of the invention still retained. In order that this may be clearly understood, in Fig. 9 I have shown an arrangement in which the adjusting rods 6' are adapted to be moved outward by their corresponding adjusting pistons 220 by admission of pressure fluid rto the inner ends of the adjusting cylinders 22| (i. e.

l the ends of said cylinders adjacent the pump while sumultaneously permitting withdrawal of fluid from the outer ends of said cylinders, and vice versa, The outer ends of the cylinders 22| are connected by a branched passage |24 and the inner ends thereof are connected by another branched passage\223, and said cylinders and passages are filled with an incompressible fluid such, for example, as oil. The output of the pump is varied and controlled by regulating the admission of uid to one of these branched passages and simultaneously regulating the withdrawal of fluid from the other. admission and withdrawal is under control of my novel and improved hydraulic follow-up which may be readily modified for use in regulating the admission andwi-thdrawal of iiuid to and from the branch passage 2| of Fig. l, as will be understood from the description which follows.

As in the embodiments previously described, the pump (Fig. 9) has a pair of laterally movable adjusting rods 6 which control the outputs of its two pumping sections. Each adjusting rod 6 is attached to its adjusting piston 220 by which it is moved and its position controlled. Each adjusting piston 220 is slidably fitted within the bore of its adjusting cylinder 22| which is closed on its inner end (that is, its end adjacent the pump I) by an end cover 222. The piston rod of each adjusting piston passes through a suitable opening in the end cover 222 of its adjusting cylinder 22|, appropriate packing being provided to prevent leakage. Each adjusting piston 220 is also modified to provide a rod 224 extending outwardly therefrom, the purpose of which will be In Fig. 9 thisA |24, which connects the l outer ends of the adjusting cylinders 22|, leads to and connects with an annular cylinder port 221 in the bore of the valve housing 225 and similarly the branched passage 2 23, which connects the inner ends of said adjusting cylinders, leads to and connects with an annular cylinder port 228 in the bore of the valve housing 225.

A valve piston 230 is slidably tted within the bore of the valve housing 225 and is formed with three heads, 23|, 232 and 233 respectively. The proportions are such that the heads 232 and 233 cover the cylinder ports 228 and 221 respectively when the valve piston 230 occupies its neutral position in which it is shown in Fig. 9, thus cutting off communication between the valve bore of the housing 225 and both ends of the adjusting cylinders 22|. Movement of the valve piston 230 to the right of its neutral position connects the cylinder port 221 with the supply ofy pressure fluid, which is admitted through the passage 236 from any suitable source such as the discharge conduit 53, and simultaneously connects the cylinder port 228 with the exhaust passage 229. Pressure fluid is then admitted to the outer ends I of the adjusting cylinders 22| and the adjusting pistons 220 are moved in an inward or deliverydecreasing direction. In the same manner, movement of the valve piston 230 to the left of its neutral position admits pressure fluid to the cylinder port 228 and the inner ends of the adjusting cylinders 22| so th'at the adjusting pistons 220 are moved in an outward or delivery-increasing direction. y

The Valve piston 230 is moved-responsive to action of my novel and improved hydraulic follow-up which will now be described. It includes a manually adjustable element here shown as an expansible Sylphon bellows 240 mounted in the bore of a containing member 24| in such manner that the parts' thereof may move freely as the axial length of said bellows 240 is extended and contracted. The right hand end of the bellows 240 abuts against the end cover 242 of the container 24| andis provided with a suitable con-V nection by which the interior of said bellows 240 is connected with a branched passage 244. The

other end of the bellows 240 terminates in a rigid end piece adapted to bear against the end of a screw 246 which extends -through a threaded opening in the closed end of the container 24| and which is provided with a handwheel 241 by which it may .be rcrtated. Rotation of the handwheel 241 in one direction advances the screw 246 into the bore of the `container 24|, causing the bellows 240 to contract inA axial length so that the volumetric capacity of its interior is reduced. Rotation of the handwheel 241 in the other directiomwithdraws the screw 246 from the bore of the container 24| and permits the bellows 240 to extend its axial length and thus inend piece adapted to abut against the end of the rod 224 of the adjusting piston 220. The' rigid A 60 crease the volumetric capacity of its interior,

pump is reduced -to its pistons 220 will continue end piece ofveach bellows 248 moves with and is moved by its rod 224 so that the position of the corresponding adjusting' vpiston 220 determines the axial length of said bellows 248,and hence the volumetric capacity of its interior. 'I'he interiors of the two bellows 248 are connected with the ends of the branched passage 244 and their sizes are such that changes in their combined interior volumetric capacities incident to movement of the adjusting pistons 220 betweentheir extreme inward and outward position is equal to or less than the maximum change which can be made in the volumetric capacity oi the interior of the bellows 240 by rotation of the handwheel 241.

A passage 245 leads from the branched passage 244 and connects with the interior of another expansible Sylphon bellows 250 positioned in the 'left vhand end of the bore of the valve housing 225. The left endof the bellows 250 abuts against the end cover 226 of the valve The interiors of the bellows 240 the tvvo'bel-A lows 248, the bellows fluid passages 244 and stantially non-compressible uid, such as oil or glycerine, and comprise the closed hydraulic follow-up circuit. i

250 and their 'connecting Upon rotation of the handwheel 241 in the' `din rection which decreases the axial length of the bellows 240. and the volumetric capacity of the interior thereof, some of the iiuid therein will be forced out into the branched' passage 244. The rods 224 present greater resistance to movement than can be overcomeby the force thus exerted thereon through the bellows 248 and hence the volumetric capacities of said bellows 248 will not change in initial response to movement of the handwheel 241. 'Ille spring 234 presents relatively small-resistance, howeve so that :duid displaced from the bellows handwheel will enter the bellows 250, increasing its axial length and moving the valve piston 238 out of its neutral position and towardthe right as viewed in Fig. 9.

As'already explained, movement of the valve piston to the .right o1' its neutral position causes d movement of the adjusting pistons 220 in an inward pr delivery-decreasing direction, thus reducing the output of the pump l.

248 will expand simultaneously with movement of the adjusting pistons 220 and their interior capacities will be increased conformably with the extent of movement of said adjustingl pistons 22o and the rods 224, permitting the entry of an amount of iuidequal to the increase thus produced in their combined volumetric ca.- pacities. Thisinward movement of the adjust- The bellows ing pistons 228 and simultaneous expansion of the bellows 248 will continue as long asthe handwheel 241 is rotated in the direction which contracts the axial length ofthe bellows 245 until, of course, the adjusting pistons 228 reach their extreme inward positions and the outputcf the minimum. when rotais stopped, the-adjusting .to move for a very tion of the handwheel slight distance and the 245 are filled with a sub- 240 by rotation of thel this inward valve piston 23|),` under influence of the spring 234, will move toward the left, contracting the bellows 250 and forcing fluid therefrom into the interior of the two bellows 248. This movement of the valve piston 230 towardthe left continues until said valve piston is restored to its neutral position and the adjusting pistons 220 are again rendered inoperative. W'hile described progressively, these movements take place almost instantaneously and there is no lag except the extremely small amount incident to movement of the valve piston 230.

Rotation of the handwheel 241 in the opposite direction permits expansion in the axial length of the bellows 240 and increase in its volumetric capacity. The spring 234 then moves the valve piston 230 away from its neutral position and toward the left as the axial length of the bellows 250 is slightly contracted and a small amount of fluid is emitted therefrom. As `already explained, this movement of the valve piston 230 causes movement of the adjusting pistons 220 in an outward or delivery-increasing direction so that the output of the pump I is increased. Restoring movement of the valve piston 230 to its neutral position takes place when the handwheel 241 is stopped and iiuid from the bellows 248 is forced into the bellows 250.

From the foregoing it will be clear that the valve piston 230 is moved out of its neutral position, in one direction or the other, responsive to movement oi the handwheel 241, which movement of the valve piston causes movement of the adjusting pistons 220, and that said valve piston 230 is restored to its neutral position by responsive movement of said adjusting pistons 220. It

. will also be clear that the volume of fluid admitted jointly to or exhausted jointly from the two bellows 248 is always exactly equal to the change in volumetric capacity of the bellows 240 so that a definite combined movement of the two adjusting pistons 220 results from each extent of movement of the handwheel 241, 4this resulting movement of the adjusting piston 220 producing a definite change in the combined outputs of the two pumping sections of the pump I whe: the operating conditions of the latter remain unchanged. Division of this movement between the two adjusting pistons 220 is immaterial as the combined outputs of the two pumping sections is unaffected thereby when said two pumping sections are of equal maximum capacities or outputs as is here presumed for simplicity of explanation. Restoration of the valve piston 230 to its neutral position is likewise unaffected by unequal movement of the adjusting pistons 220, this restoration taking place whenever the changes in the combined volumetric capacities of the two bellows 248 equals the change in the volumetric capacity of the bellows 240, regardless of whether the volumetric capacities of the two bellows 248 are changed 'in equal or unequal amounts.

In a similar manner'the follow-up acts t'o correct for any displacement of the adjusting pistons 220 which could alter the output of the pump I from the output corresponding to any particular position inhwhich the handwheel is held stationary. For example, with the handwheel 241 stationary,l if vone of the adjusting pistons 220 moves outwardly, as because'of leakage or otherwise, and the other adjusting piston likewise moves outwardly or remainsl stationary, an increase in the output of the pump I would result unless corrective action is set in motion.v Such movement of one or both adjusting pistons 220 will, however, cause corresponding contraction of metric capacities of the two bellows 248 againV equal the proper amount as determined by the bellows 240 and the handwheel 241, when the valve piston 230 will again be restored to its neutral position, this corrective action also having reduced the output of the pump I to the amount as determined by the position of the handwheel 241. Corrective movement of the adjusting pistons 220 is thus brought about whenever the combined capacities of the two bellows 248 is either increased or decreased by'movement of one or both of the adjusting pistons which does not occur responsive to movement of the handwheel 241. The follow-up therefore functions not only to produce a definite output of the pump I (when operating conditions of said pump I remain unchanged, as is presumed throughout the explanation of the embodiment of Fig. 9) for each position of the handwheel 241, but also functions to continuoufsly maintain such definite output.

The handwheel 241 may thus be rotated to cause any desired change in the ,capacity of the vbellows 240 and hence to cause anyl desired outputI of the pump l so tha'. the output of said pump I may be innitely varied from minimum to maximum. The output of the pump I, comprising the combined outputs of its two'pumping sections, may thus be accurately controlled throughout the entire range of its adjustment. This control, which is effected independent of definite control of the output of either of the two pumping sections and without control of the division of the combined outputs between the two sections (except, of course, at maximum and minimum outputs), is accomplished. by a single control valve common to both adjusting cylinders 22| and which regulates the joint operation of both adjusting pistons 22o by regulating the nuid l My limproved hydraulic follow-up has many,

advantages. One of these is that it is free from Ilost motion as the spring 234 takes up al1 play between the parts and continuously maintains a substantially constantl pressure in the followup circuit. The parts are inexpensive and may be made'of relatively light material as they are subject to no load except that due to the pres sure in the follow-up circuit, which pressure is never high and cannot, `in fact, exceed the amount determined by the spring 234; the parts lare protectedv against Ithe'appli-cation of any external fluid pressure* by the drain or exhaust con-1 nections 243 in the .bores housing the two bellow 248 and the exhaust connection adjacent the bel to any desired extent, thus facilitating convenient location of the manual control member and making the follow-up well suited for use as a remote control.

When it is desired to use my. improved hydraulic follow-up vin connection with the adjusting cylinder and spring-loaded adjusting piston arrangement `of Fig. 1, the branch passage 2| is connected with the annular cylinder port 221 in the bore of. the valve housing 225 and the annular cylinder port 228 is suitably closed or may be omitted. With this arrangement the head 23| and the reduced portion of the'va-lve piston intermediate the heads 23| .and 232 may also be omitted, thus simplifying the structure and reducing its size, as the end of the bellows 250 will .then be adapted to bear against the adjacent The operation of this modend of the head 232. ified arrangement will be understood from -the explanation already given. 1

Afurther'modification of the mechanism for regulating the-admission of uid toand withdrawal of fluid from vthe branch passage 2| is illustrated in Fig. 10. The operation of this regulating mechanism is responsive to pressure of the fluid in the discharge conduit 53v and it functions to so regulate theadmission and withdrawal of fluid from .the branch passage 2| that the output of the -pump is altered to maintain a substantially constant predetermined, pressure in said discharge conduit. v l y The branch passage 2| of Fig.' 10 connects with an annular cylinder port 265 in the bore of the valve housing. Admission and Withdrawal' of fluid to and from the branch passage 2l are controlled by the head 269 of the valve piston which is slidably fitted within the valve bore. so that, as in previously described arrangements, a single element'serves tov regulate the volume of fluid admitted jointly to the outer .ends of the adjusting cylinders or withdrawn jointly therefrom.-

The arrangement is such that the head 269 closes the cylinder port 265 and completely cuts oi communication between the branch passage 2| and the valve bore when the valve piston occupies its neutral position in vwhich it is shown in Fig. 10. Movement of the valve piston to 'the left of i-ts neutral position admits pressure uid from the discharge conduit 53 .to the branch passage 2|, thus causing the adjusting pistons l0 to move inward. to reduce the pumps output; pressure iiuidfrom the discharge conduit is supplied to the valve bore as through a passage 213 which connects with said valve bore at a point intermediate the heads 261 and 269 of the valve piston. When the valve piston is moved to the right of its neutral position, uid may pass from the branch passage 2| into the left end-'of the valve bore, through the exhaust passage 264 and to the reservoir 52, so that the adjusting pistons I6 'are moved outward to increase the pumps output, this piston movement taking place under inuence -of the springs |2 and of pump pressure acting upon Ithe-inner ends of .the slides 1, as already explained. The head 269 is shown as pro 'ded with conventional V-notches on each end t eref to provide gradual connection ofthe cylinder port 265 with the supply of pressure fluid and/with the exhaust passage respectively when the valve piston moves .to the lett and Ito the right of its neutral position. The right hand end 263 of lthe valve bore is also connected with the exhaust passage 264 to prevent building up of pressure therein, .this connection being here shown as through .the cover 26| which closes .the right hand end of said .valve bore.

Movement of the valve piston takes place responsive to change in pressure of the fluid in the discharge conduit 53 and its position in the valve bore is determined by the pressure in said discharge conduit relative to a pre-'determined pressure value therein. This is Aaccomplished by making the diameter of the head 269 greater than the diameter of the head 261 which is slidably iitted'in-the reduced portion of the valve bore, so that pressure of the iiuid lfrom the discharge conduit which is admitted to the valve bore intermediate these two heads exerts a force upon the valve piston tending4 -to -move said valve piston toward the left in opposition' to the force exerted upon the valve piston' by the spring 210 which tends to move said valve piston tov Ward the right. It will thus be .seen that the valve piston occupies its neutral position, vin which the head 269 closes the cylinder port 266, only when the :duid pressure in the discharge conduit 53 has a denite value as determined .by the spring 210, the compression of which may be adjusted by means of the screw -212 which extends through the end cover 262 of the valve housing and the inner end of which bears against the abutment piece 21| intermediate said screws inner end and the spring 210. It will also be understoodl that increase in .pressure of the uid in the discharge conduit 53 above the value determined by the spring 216 will increase the huid-exerted force urging the lvalve piston toward the left, so that said valve piston will be displaced to the left of its neutral position, causing the adjusting pistons ||J to move inward to decrease they pumps output. Conversely, decrease in pressure of vthe uid in the discharge conduit 53 below thevalue determined bythe l spring 210 will decrease the fluid-exerted force active in opposition to the force exerted by said spring and said spring 210 will immediately displace said valve piston to the right of its neutral position, permitting withdrawal or exhaust of rluid from the branch passage 2|, whereby the adjusting pistons l0 will be moved outward or in a delivery-increasing direction. In either case, the valve piston will be restored to its neuvtralvposition and movement of the adjusting pistons will cease upon re-establishment of the predetermined pressure value-in the discharge conduit 53, as will in many instances result from corrective change in the pumps output.

In this manner the valve piston is moved, responsive to change in pressure of the uid in the discharge conduit, rto sov regulate admission and withdrawal of uid to and from the branch passage 2| that the output of the pump is automatically altered, within-its capacity range, to provide a delivered vvolume at which the pressure of the uid in the discharge conduit is "held sub stantially constant at a pre-determined value.

As in the embodiments previously described, each adjusting piston l0 is independently movable to control the output of its pumping section and there are an almost infinite number of combinations of relative positions of the adjusting pistons I0 and their attached adjusting rods 6 which these parts mayoccupy at any intermediate output of the pump I. As in the previously described embodiments, relative division of the pumps output between its two pumping sections is not controlled and does not affect the control of the pumps output as the combined outputs will be held at the proper total amount required to produce the pre-determined pressure in the discharge conduit irrespective of the proportion of this total contributed by each pumping section. This control independent of definite control of the output of either of the two pumping sections (except, of course, at maximum and minimum outputs) and is accomplished by a single control valve mechanism common to both adjusting cylinders Il and which regulates the joint operation of both adjusting pistons I by regulating the fluid volume admitted jointly to or expelled jointly from the passage and said adjusting cylinders I l In the embodiment of Fig. l1 the floating pistons I0 are disposed in the same cylinder Il', with the springs I2 disposed between'the ends of the cylinder and the respective pistonsand the piston rods 6' The piston rods 6 may be connected in any suitable manner with the delivery-determining members 6 of the pump sections or units; these connections being omitted for convenience in illustration. The piston and cylinder arrangement of Fig. ll may be employed with any ofthe previously described output control means but for convenience manually adjustable means similar to that illustrated in Fig. 8 is shown. These means comprise the master cylinder 200 and the handwheel 201 for either introducing more fluid to or exhausting fluid from the passage 2l and the double cylinder Il. The ends of the double cylinder are connected by a passage I23 leading to the exhaust. The pistons I0, as described above in connection with the other modifications, float between the pressures generated by the pump sections and each Ais free to assume a position 'in balanced relation through the flexible hydraulic transmissionbetween the pistons exteriorly of the pumping sections. By rotating the manually adjustable wheel 201 in oppositie directions more of the incompressible fluid may be supplied to the passage 2l and the double cylinder or fluid may be exhausted therefrom, which operation causes corresponding movements of the adjusting pistons IIJ.

It will be understood that the several embodiments of my invention have been described for the purpose of llustrating the operation and construction of the apparatus of my present invention and that changes may be made without departing from the spirit of the invention.

I claim:

1. In a rotary piston pump unit of the multisection type discharging into a common chamber wherein diametrcally opposite delivery determining elements are movable radially inwardly against the pressure or pressures of the pump sections to decrease their deliveries, and a control thereof, in combination, diametrcally opposed fluid pressure cylinders in alinement with said elements, pistons in said cylinders operatively connected with said elements, a fluid pressure passage connecting the outer ends of said cylinders, said passage and outer ends of said cylinders containing an incompressible fluid and means for forcing additional fluid into said passage and said cylinders against the pump section pressures and for permitting the exhaust of the fluid therefrom. v

2. In a rotary pump comprising two separate extending out from the pistons.

of output is therefore effected I pump sections discharging into a common chamber wherein radially movable elements vary and determine the outputs per revolution of said sections, and a control thereof, in combination, apair of separate fluid pressure pistons .operatively connected with-said elements, said elements and said. pistons being urged in the delivery increasing direction by the internal pressures of the pump sections, an adjustable incompressible fluid circuit connecting lsaid pistons exteriorly of the pumping sections, said incompressible fluid exerting forces on said pistons in opposition to the pressures generated by the pump sections, and means for forcing fluid into said circuit against the pump pressure and to permit the exhaust of uid therefrom responsively to movements of the pistons by the pump pressures.

3. In a rotary piston pump unit of the multisection type discharging into a common chamber wherein diametrcally opposite delivery. determining elements are movable radially inwardly against the pressure or pressures of the pump sections to decrease the delivery, and a control thereof, in combination, diametrcally opposed fluid pressure cylinders in alinement with said elements, pistons in said cylinders operatively connected with said elements, springs behind said pistons urging them in the direction of the force exerted by the pump internal pressures, a. fluid ypressure passage connecting the outer ends of said cylinders, said passage and outer ends of said cylinders containing an incompressible uid, and means for forcing additional fluid into said passage and said. cylinders against the pump pressures and the springsiand for permitting thc exhaust of the fluid therefrom.

4. In a rotary piston pump unit of the multisection type discharging into a common chamber wherein each section is provided with a delivery varying element which is urged in one direction by the pressure generated in the corresponding pump section, in combination, fluid pressure pistons operatively.y connectedwith said elements to move in unison therewith, an incompressible uid circuit connecting saidpistons, said incompressible fluid exerting forces on said pistons in opposition to the pressures generated by the pump sections and means' for forcing fluid into said circuit against the pump section pressures and to permit the exhaust of uid therefrom responsive- 1y to movements of the pistons by the pump pressures.

5. In a rotary piston pump unit of the multisection type discharging into a common chamber ywherein each section is provided with a delivery varying element which is urged in one direction by the pressure generated in the corresponding pump section, in combinaion, a pair of separate fluid pressure pistons operatively connected with said elements to move in unison therewith, an incompressible fluid pressure circuit connecting said pistons exteriorly of the pumpwith each piston being thereby floatingly balanced between the pressures generated in the separate pump sections, and means for varying at will the length of said incompressible fluid circuit.

6. In a rotary piston pump unit of the multisection type discharging into a common outlet wherein diametrcally opposite delivery determining elements are movable radially inwardly against the pressure or pressures of the pump nsections to decrease their deliveries, and delivery control means therefor, in combination, dia.- metrically opposed fluid pressure cylinders in alinement with said elements, pistons in said cylindersoperatively connected with said elements, a fluid pressure passage leading to the outer end of each cylinder and containing a uid adapted to hold the piston of the corresponding 7. In a rotary piston pump unit of the multisection type discharging into a common outlet wherein each section is provided with a delivery varying element which is urged in one direction by the pressure generated in the corresponding pump section, in combination, a pair of separate fluid pressure pistons operatively connected with said elements `to move in unison therewith,

`each of said pistons being operated by uid pressure against the pressure generated in the corresponding pump section to vary the posilcorresponding demeans for varying pressures generated tions of the pistons and the livery varying elements and the uid pressure opposed to by the pump sections.

8. A rotary piston pump unit' of the multisection type discharging into a common outlet wherein diametrically opposed delivery determining elements are movable radially inwardly against the pressure lor pressures of the pump sections to decrease their deliveries, comprising diametrically opposed fluid pressure cylinders in alinement with said elements, piston elements in said cylinders for operating said delivery determining elements, and self-alining operative connections between said elements and said pistons, said self-alining operative connections each including a member positioned intermediate the piston element and the corresponding delivery determining element, said member having on one of its ends a at surface engaging one of said elements and said member having on its other end a spherical member engaging the other of said elements.

9. A rotary piston pump unit of the multi-section type discharging into a common outlet wherein diametrically opposed delivery determining elements are movable radially inwardlyl against the pressure or pressures of the lpuinp sections to decrease their deliveries, comprising diametrically opposed fluid pressure cylinders in alinement with said elements, a piston element in each cylinder foroperating the corresponding delivery determining elements, and a self-alining operative connection between each delivery determining element and its corresponding piston element, said operative connection comprising a bearing member having a flat face in engagement with one of said elements and an engaging surface of arcuate form with the other of said elements.

10. A rotary piston pump unit of the multisection type discharging into a common outlet wherein diametrically opposed delivery determining elements are movable radially inwardly against the pressure or pressures of the pump sections to decrease their deliveres, comprisingl diametrically opposed fluid pressure cylinders in alinement with said elements, pistons in said cylinders for operating said delivery determining elements, and self-alining operative connections between said elements and said pistons, each of said pistons having a guiding skirt and a spring n by a. multi-section pump,

surrounding the delivery determining element and urging the delivery determining element and the piston radially outward.

l1. A rotary piston pump unit of the multisection type wherein diametrically opposed delivery determining elements are movable radially inwardly against the pressure or pressures of the pump sections to decrease their deliveries, comprising an intake for each section, diametrically opposed uid pressure cylinders in alinement with said elements, pistons in said cylinders exposed to pressure fluid only in the outer ends of said cylinders and operatively connected with said elements, and means for maintaining at the inner end of each cylinder and piston a relatively low pressure substantially equal to the pressure of the uid in said intakes comprising connections between the inner ends of said cylinders and at least one of said intakes.

12. In mechanism for controlling the volume of uid delivered to a common discharge conduit by a multi-section pump, a separate output-determining element for each -section independently movable to vary the output thereof independent of the outputs of the other sections, a separate fluid motor for each of said sections adapted to actuate the output-determining element thereof, the operation of each of said fluid motors in one direction of its movement being responsive tothe admission of pressure fluid thereto and in the other direction of its movement being responsive to the emission of uid therefrom, and valve mechanism common to all of said uid motors for regulating the volume of pressure fluid admitted jointly to all of said fluid motors and the volume of fluid expelled jointly therefrom, whereby the volume cf fluid delivered to the common discharge conduit by all of said pumping sections is controlled irrespective of the portion thereof contributed by each of said sections at outputs intermediate the maximum and the minimum combined outputs of all of said sections.

13. In mechanismfor controlling the volume of fluid delivered to a common discharge conduit a separate outputdetermining element for each section independently movable to vary the output thereof independent of the outputs of the other sections,

separate independently operating power means for each of said sectionsadapted to actuate the output-determining element thereof, and control means common to all of said power means for regulatingthe extent of the combined operation of all of said power means without predetermined control of the extent of operation of any one of them, whereby the volume of fluid delivered to the-common discharge conduit `by all of said sections is controlled irrespective of the division thereof between said pumping sections at outputs intermediate the maximum'and the minimum outputs of all of said sections. r

14. In mechanism for controlling the volume of fluid delivered to a common discharge conduit by a plurality of variable output pumping units, a separate output-determining element for each of said units independently movable to vary the output thereof independent of the output of the others of said units, a separate uid motor for each of said units adapted to actuate the outputdetermining element thereof, the operation of each of said fluid motors in one direction of its Amovement being responsive'to the admission of pressure duid thereto and in the other direction of its movement being responsive to the emission of fiuid therefrom, and valve mechanism commonk to all of said fluid motors for regulating the volume of pressure fluid admitted jointly to all of said fluid motors and the volume of fiuid expelled jointly therefrom, whereby the volume of fluid delivered to the common discharge conduit -by all of said pumping units is controlled irrespective of the portion thereof contributed by each of said pumping units atoutputs intermediate the maximum and the minimum combined outputs of all of said units, said valve mechanism including a valve element active to control admission of pressure fluid to and emission of fluid from said fluid motors and movable responsive to'fluid pressure existing in` the discharge conduit relative to a predetermined pressure therein, said element occupying a neutral position at which the combined outputs of said pumping units is unchanged when said'predetermined pressure exists in said discharge conduit, said element moving in one direction away from its neutral position to cause l operation of saidfluid motors in a direction whereby the combined outputs of said pumping units vis decreased responsive to pressure in said discharge conduit in excess of said predetermined pressure and said element moving in the other direction away from its neutral position to cause operation of said uid motors in a direction whereby the combined outputs of said pumping units is increased responsive` to pressure in said discharge conduit below said predetermined pressure.

15. In mechanism for controlling the output of a double pump comprising two pumping sections, said pumping sections having a' common discharge conduit and the combined outputs of said pumping sections constituting the output of said double pump, a separate output-determining element for each of said pumping sections independently movable against the fluid pressure generated in the corresponding pumping section tov vary the output of its pumping section independent of the output of the other pumping section, a separate fluid` motor for each of said pumping sections adapted to actuate the output-determining element thereof, the operation of each of said fluidmotors being responsive to the admission of pressure fluid thereto and the emission of fluid therefrom, and valvemechanism common to all of said fluid motors for regulating the volume of pressure fluid admitted jointly to and the volume of uid expelled jointly from all o f said motors4 whereby the output of said double pump is controlled irrespective of the portion thereof contributed thereto by each of said pumping sections at outputs intermediate the maximum and minimum output of said double pump.

16. In mechanism for controlling the output of a double pump comprising two pumping sections, said pumping sections having a common discharge conduit and the combined outputs o'f 'said pumping sections constituting the output ofsaid double pump, a separate output-determining element for each of said pumping sections independently movable to vary the output of its pumping section independent of the output of the other; pumping section, a hydraulically-actuated piston for each `of said pumping sections movable against the uid pressure generated in the corresponding pumping section to actuate the output-determining element thereof, movement of each of said pistons being responsive to admission of fluid to and emission of fluid from the adjusting cylinder thereof, and means common to the cylinders of both of said pistons for regulating the volume of fluid admitted jointly to and emittedjointly from one side of each of said pistons, whereby the extent of the combined movement of both of said pistons is varied without individual control of the extent of movement of either of them, thereby controlling the output of said double pump irrespective of the division thereof between said pumping sections at outputs intermediate the maximum and the minimum outputs of said doublepump.

, 17. In mechanism for controlling the volume of fluid delivered to a common discharge conduit by a plurality of variable output pumping units, a separate output-determining element for each of said units independently movable to vary the output thereof independent of the output of the others of said u nits, a separate fluid motor for each of said units adapted to actuate the outputdetermining element thereof, the operation of each of said fluid motors being responsive to the admission of pressure fluid thereto and the emission of fluid therefrom, and valve mechanism common -tol al1 of said .fluid motors for regulating the volume of fluid admitted jointly thereto and the volume of fluid expelledjointly therefrom,

f whereby the volume of fiuid delivered to the common discharge conduit by all of said pumping .units is controlled irrespective of the portion thereof contributed by each of said pumping units at outputs intermediate the maximum and the minimum combined outputs of all of said units, said valve mechanism including a control valve having a piston movable under control of a. hy-

draulic follow-up to regulate admission of fluid toand emission of fluid from said fluid motors,

said hydraulic follow-up comprising a closed fluid circuit having a first fluid chamber the volumetric capacity of which is variable to cause 'operation `of said fluid motors, a separate fluid chamber for eachL of said units the volumetric capacity of which varies simultaneously with and responsive to operation of the fluid motor thereof anda fluid chamber the volumetric capacity of which .varies responsive to-changes in thevolumetric capacities of said other chambers and active thereupon to cause movement of said valve piston, and means for varying the volumetric capacity of said first named chamber.

18. In mechanism for controlling a plurality of variable output pumping units, a separate fluid motor for each of said units for varying the output thereof, each of said uid motors comprising a piston which is operated -by the admission and exhaust of fluid pressure from the opposite sides thereof, a valve for controlling the exhaust and admission of fluid pressure, an adjustable hydraulic circuit to which said valve is operatively responsive, operative connections between the pistons and said circuit and means for adjusting the said circuit at will to alter the combined outputs of the said pumping units. 19. In a control mechanism for the combined outputs of a plurality of variable-output pumping units having a common discharge conduit, a separate output-determining element for each of said units movable to vary the output thereof independent of the output of said other units, a

separate fluid motor for each of said units adapt-- ed t'o actuate the output-determining element thereof, the operation of each of said fluid motors being responsive to admission of fluid thereto and emission of fluid therefrom, andmeans common to all of said fluid motors for regulating the 

